Scientists have long been unsure as to exactly how the brain tracks time. Theories abound — one is that the brain has a cluster of cells specialized to count off intervals of time. Another is that our internal clock is just a wide array of neutral processes. Gal Zauberman, an associate professor of marketing at the Wharton School of Business, recently led a team of investigators to better understand how our brain processes time perception.

Apparently, it all seems to be about how actively engaged your brain is when making a memory. All studies seem to agree that the brain does not do a good job of tracking longer intervals of time. When you are bored — say, stuck on a plane without anything to distract you from the hum of the engines — time really can seem to slow down. But when you are actively engaged in an interesting, stimulating task, it seems that time moves faster.

Studies have also found that extremely emotional events — a breakup, a birth, a death — can seem like they happened just yesterday, even if they happened decades ago.

They key to the differences on how we perceive time seems to be based on how you think about an event. In the words of philosopher Martin Heidegger “time persists merely as a consequence of the events taking place in it.” But Zauberman points out that the opposite may also be true. According to the report, if very few events come to mind, then the perception of time does not persist. The brain, in a sense, telescopes the interval that has passed.

The study went down like this: Zauberman led a team of investigators who tested college students’ memories of a variety of news events. These illustrious events included the appointment of Ben Bernanke as chairman of the Federal Reserve (33 months before the study) and Britney Spears’s decision to shave her head (20 months). What they found was that, on average, the students underestimated how much time had passed by three months.

But the study also found that the way the brain fixes the relative timing of events depends on memory. Apparently, if there are more intervening events between “major” occurrences — such as Bernake’s appointment of the trails of Britney Spears — the more “in the past” the original event seems to be. As Zauberman puts it, “People have a hard time understanding the passage of time, and in order to understand it latch onto something we do understand — the unfolding of events.”

It seems that your sense of enjoyment of events comes into play. Psychologists discovered that when people were tricked into believing that more time had passed than was really the case, they thought they must have been having more fun. Therefore, they did things like enjoy music more. They were even less annoyed at performing menial tasks.

Psychologist Aaron M. Sackett tells us that “the mind is a wonderful sense-making device, that it takes ambiguous or confusing information and simplifies it according to rules of thumb.” Sackett, who co-led the study, points out that we have to rely upon our own beliefs to make sense of the difference.

So does time really fly when you’re having fun? In short, it would seem so.